Effect of cationic disorder on the spin polarization in FeMo double perovskites

Abstract

Ordered Sr2FeMoO6 is expected to have complete spin polarization, however all samples usually present some degree of Fe/Mo disorder which reduces the tunneling magnetoresistance in granular samples. It can be inferred that disorder is detrimental to the half-metallicity. We present an electronic approach of this disorder using a model based on a correlated electron picture with localized Fe-spins and conduction electrons interacting with the local spins via a double-exchange–type mechanism. This succeeds in stabilizing a ferromagnetic ground state in the absence of disorder. Disorder is treated within the dynamical mean-field approach which is equivalent to the coherent potential approximation. We shall show how electron disorder affects the density of states and the ground-state properties with a particular emphasis on the spin polarization.